Figure 5. Normalized change between future and historic
simulations
(\(100\times\frac{\text{future}-\text{historic}}{\text{historic}}\))
for the 41 HPEs analyzed. Events are sorted by the change in rainfall
accumulation (blue bars). Dashed lines represent average inter-event
values (written also inside the legend). The non-normalized changes are
shown in Fig. S4. Correlations between the change in rainfall
accumulation and the three other parameters are in Fig. S5.
3.3.1 Spatial Concentration of Future Rainstorms
To better understand the changes in the rain area, we examine its
changes using a range of rain rate thresholds. Divergent changes in the
extent of areas exceeding various rain rates are essential in
understanding possible hydrological responses to climate change (Bacchi
& Ranzi, 1996; Fowler, Lenderink, et al., 2021; Peleg et al., 2018).
Fig. 6a displays the event-average areal rainfall coverage for each HPE
with different rain rate thresholds, normalized by the largest coverage
for each intensity for both historic and future simulations. The
fraction of events with larger areal coverage for each rain rate
threshold in historic events, i.e., the relative number of points below
the 1:1 line, is displayed in Fig. 6b. The areal coverage of rainfall
with relatively low rain rates (0.1-5 mm h-1) is
reduced significantly for future compared to historic simulations. The
opposite case is true for high rain rates (20-100 mm
h-1). This change occurs at rain rates of
~10 mm h-1, where no significant
change is documented between rain area above this threshold in historic
and in future simulations.
These different trends imply that when compared with historic
rainstorms, the total “wet” area in future events is lower, and the
storms are more concentrated around the higher rain rates. This
conclusion is further strengthened by the change in the autocorrelation
pattern of convective rainfall, which demonstrate a much sharper
decrease with distance in future compared with historic simulations and,
accordingly, the median of the autocorrelation distance decreases from 8
km to 5 km (Fig. S6).